Thanks for the information Newt. I managed to find some old window screens that I could recycle so I went ahead and included the screen in the containers.

What else would work to stop/minimize soil loss in a similar situtation? I've read that coffee maker filters are sometimes used, but I don't drink coffee and so I have no filters kicking around. I'd be really interested in alternatives (to the screen) that I can scrounge or re-use.

You are so very welcome! I've used bits of broken pots, small stones from the garden, used dryer sheets - unscented as well as the coffee filters and old screen and landscape fabric. If the hole is not especially large, I find that the soil compresses enough that I don't bother with anything in the bottom of the pot.